This invention relates to a servomotor control system in which a velocity loop computation and a current loop computation for controlling a servomotor are performed by a microprocessor. More particularly, the invention relates to a servomotor control system for accommodating the load on the processor with the response of the computations in each of the loops.
An arithmetic circuit such as a microprocessor has recently come to be employed for controlling a servomotor. It is required that the microprocessor execute at least a velocity loop computation, in which a current command is computed from an offset velocity (which is the difference) between a commanded velocity and the actual velocity of the servomotor), and a current loop computation, in which a command for application to the current drive circuit of the servomotor is computed based on a difference between a current command and the armature current of the servomotor.
In order to obtain a desirable servomotor operating characteristic, it is required that the response characteristic of the current loop be quicker than that of the velocity loop. Since there is interference between current and velocity ascribable to a reverse electromotive force in a servomotor, the velocity loop and current loop computations cannot be rendered independent of each other and both computations must be executed at a predetermined sampling period. The result is a burden upon the microprocessor in terms of processing time.